1. Field of the Invention
The present invention relates to an interpolation address generating method and interpolation address generating device for a recording medium recorded with addresses completing single frames.
2. Description of Related Art
Compact Disc (hereinafter referred to as "CD") data recording formats for, for example, Digital Audio Compact Discs (hereinafter referred to as "CD-DA") or video CD's etc. are constructed so that a single frame becomes the minimum unit, with 98 frames constituting a single block, as shown in FIG. 4.
One frame is constructed from 588 bits, with the leading 24 bits being provided for synchronization data, the following 14 bits being provided for a sub-code data area, and the subsequent bits being provided for data and parity.
With frames of this structure, a single block is constructed from 98 frames and sub-code data is gathered from the 98 frames to form the kind of single block sub-code data shown in FIG. 5(a).
The sub-codes taken for the leading first and second frames, i.e. frame 98n+1 and frame 98+2, of the 98 frames are taken to be the synchronization pattern. Each item of 96 bit channel data, i.e. the sub-codes for P, Q, R, S, T, U, V and W, is formed using the third frame through the 98th frame i.e. frame, 98n+3 through frame 98n+98.
Of these, the channels P and Q are used for controlling accesses. More specifically, channel P only indicates the pause portion between tracks, with finer control being carried out by the channel Q, i.e. Q1 to Q96. The 96 bits of Q channel data are structured in the way shown in FIG. 5(b).
First, the bits Q1 to Q4 are taken for control data and are used for audio data channel numbers, emphasis and CD-ROM identification etc.
The bits Q5 to Q8 are then taken as an address to be used as the sub-Q data control bits. If the value for these four bits is "0001", this indicates that the sub-Q data for the following bits Q9 to Q80 is audio Q data. A value of "0100" indicates that the sub-Q data for the following bits Q9 to Q80 is video Q data.
The bits Q9 to Q80 are regarded as 72 bit sub-Q data, with the remaining Q81 to Q96 being a Cyclic Redundancy Code (hereinafter referred to as CRC) which is used for determining the validity of the received Q-channel data so that only correct data is read-out.
In this format occurring in the aforementioned Q-channel frame structure, hours, minutes and seconds showing the address within the disc are discretely recorded within the sub-code so as to conclude the 98 frames. There is also a high degree of reliability with respect to errors such as burst errors because the channel Q recorded with the hours, minutes and seconds also has the 16 bit CRC attached.
Next, an example of a disc system with an address recorded within a single frame is shown. FIG. 6 is a schematic view of one sector. As shown in the drawing, one sector is constructed from n frames, with the leading bits being taken as the sector synchronization, followed by the sector header. The sector address is recorded at this sector header. The data area to be played back and the parity area are then recorded after this sector header.
The sector header is constructed from 32 bytes laid out, for example, in the manner shown in FIG. 7. i.e. the leading 16 bits are taken as the CRC, with the following 24 bits comprising an "address" field recorded with a serial address. The most significant bits (hereinafter referred to as MSB's) of the "address" field are taken to be "address" field 1 and the least significant bits (hereinafter referred to as LSB's) are taken to be "address" field 0.
This "address" field is coded in two's compliment, with the initial sector present in the program area being taken as address "0" and the final sector present in the read-in area being taken as address "1".
Following the address field, the 32 byte header sector is constructed from a "Reserved" field, a "layer" field, a "Copyright" field, a "Track Number" field, an "Index Number" field, a "Reserved" field, a "Timecode" field, an "application code" field and an "application data" field, etc.
In a CD playback system, each type of control is carried out using the address (in hours, minutes and seconds) as a reference. For example, when there is a pause in playback, control is exerted so as to jump one track in the direction of the inner periphery every time the same address is played back. With a CD-DA and video CD, a disc address, i.e. hour, minute and second, is recorded within the Q-channel sub-code concluding the 98 frames, and because 16 bits of CRC code are attached there is good resistance to burst errors.
However, in the kind of disc system shown in FIG. 6 where a sector address is recorded so as to conclude a single frame, a high degree of reliability with regards to errors such as burst errors cannot be obtained even if a CRC is attached.
If, for example, a sector address within the sector synchronization "Sync" or the sector header is missed when data is played back in the disc system shown in FIG. 6 where a sector address is recorded within a single frame, the data becomes corrupted. Corruption in a small portion of the played back data will have little effect if audio data is recorded in the data area because the audio is muted during a pause.
However, if video data is recorded in the data area, the image outputted as a result of the image signal disappears and picture omissions occur. These picture omissions are very noticeable on the screen and make viewing difficult.
In the above, an example has been given where the sector address of an image data signal has been corrupted but data corruption with regards to other kinds of data may also hinder normal operation.